Many industrial processes involve operations in which active ingredients are delivered in compositions carried by organic solvents. Due to environmental concerns, manufacturers have been seeking to discontinue the use of organic solvents and substitute water as the carrier of the active ingredients. Organic solvents tend to be at least somewhat toxic and contribute to air pollution, e.g., by creating smog. Additionally, some volatile organics are known to be catalysts in the destruction of ozone in the upper atmosphere, particularly dichlorodifluoromethane and trichlorofluoromethane, which have been used extensively in propellants for aerosols and as blowing agents.
Particular compositions where active ingredients are carried by a liquid include mold release compositions which are sprayed, or otherwise applied onto the surface of a mold so that the product to be made in the mold may be readily removed therefrom. The major components of such compositions have been a solvent and an active ingredient, such as a release lubricating agent or another solvent. Previously, most mold release compositions included volatile organics as solvents which normally make up about 90.0% to about 99.5%, by weight, of the compositions, and most commonly about 95.0% by weight.
In some mold release compositions, water has been used as a carrier in which the active ingredient and water is used in place of volatile organic solvents. Additional agents such as emulsifiers and wetting agents have also generally been used in such compositions. Water is not considered a solvent in such compositions because active ingredients are generally insoluble in water; however, the water serves the same basic function as the organic solvent did--to deliver the active ingredient. These compositions have been used in rubber-processing plants and have been used recently to release some plastic and polyurethane parts.
Water has several distinct advantages over organic solvents in its use as a carrier, in that it is non-toxic, environmentally friendly and inexpensive. On the other hand, water has some significant disadvantages as a replacement for organic solvents in liquid compositions used to deliver active ingredients (hereinafter "delivery compositions"). Water does not coat most surfaces evenly since it is repelled by many materials, e.g., metals, plastics, and glass. Rather, water tends to form beads or droplets on surfaces so that, when the water evaporates, the compounds dispersed in the water are deposited unevenly on the surface. The addition of surfactant and other similar substances to the delivery compositions is only partially successful in eliminating this problem.
Additionally, most compounds that are used as active ingredients, such as lubricating or release agents, are relatively immiscible in water. Substantive amounts of emulsifiers, surfactants or other substances have had to be used with the water to mix these otherwise immiscible ingredients together. Emulsifiers and surfactants are normally non-volatile, chemically modified fatty acids and other compounds that have segments of the molecule that are soluble in the water and segments that are soluble in the material to be suspended, e.g., ethoxylated fatty acid esters. Since emulsifiers and surfactants are not volatile, they remain with and mix with the active ingredient(s) when the water evaporates. They are usually present in amounts up to 10 to 20% of the active ingredient and may interfere with the operation of the active ingredient. In addition, the surfactants or emulsifiers may be chemically unstable under tile conditions of use and may decompose due to heat or for other reasons with deleterious results.
Attempts to solve this problem by adding less emulsifier to the water to minimize emulsifier build-up and by adding water soluble solvents which have been only partially successful because the emulsion or dispersion becomes less stable and the active ingredients tend to separate.